Aromatic polyimides (PI) are generally considered not readily processable via conventional thermoplastic or hot-melt techniques. These polymers are, however, exceptionally thermally stable as well as resistant to attack by solvents, and they exhibit high glass transition temperatures. Polymers of the polyphenylene oxide (PPO), polyphenylene sulfide (PPS), and polyphenylene sulfone (PPSO.sub.2) classes are generally more processable than the polyimides by the thermoplastic or hot-melt techniques. However, all of these systems (referred to as PPX polymers hereinafter) are generally more susceptible to attack by solvents and have lower glass transition temperatures than polyimides. Thus, attempts have been made to incorporate the best attributes of both the PPX and PI systems into a single polymer system without the inherent drawbacks of either of the individual PPX or PI systems.
Williams, III, U.S. Pat. No. 3,933,749 attempts such a solution by incorporating sulfur linkages into a polyimide backbone. Takekoshi, U.S. Pat. No. 4,281,100 teaches the use of particulated oligomeric polyetherimide acids which may be converted to a high molecular weight polymer system by melt polymerization. Williams, III et al, U.S. Pat. No. 3,983,093 discloses the use of varied proportions of different polyetherimide segments in an attempt to reach the optimum balance between processability and solvent resistance. The polymers of the above cited patents, however, retained an undesirable level of susceptibility to attack by certain solvents. For instance, Williams, III et al, U.S. Pat. No. 3,983,093, col. 8, lines 25-31, discloses the solvent resistance of several polymers of that patent. Notably, relatively low solvent resistance was obtained in methylethyl ketone. Structurally, all of these polymer systems have employed para-oriented ether linkages and/or short phenylene oxide groups.
Furthermore, the processes employed to produce these polymers have required process conditions involving high temperatures, high pressures, and/or inert atmospheres. Such conditions obviously add to the cost of the process, and therefore to the cost of the final product. Thus, there is a definite need in the art for a polyether with imide linking units having high solvent and thermal resistance while retaining processablity. There is also a need in the art for a process for producing such a polymer which does not require severe reaction conditions.
Accordingly, an object of the present invention is to provide solvent resistant polyphenylene ethers.
Another object of the invention is to provide polyphenylene ethers with good thermal stability.
Yet another object is to provide polyphenylene ethers with imide linking units which are processable by hot melt techniques.
A further object is to provide polyphenylene ethers with imide linking units which are moldable by injection molding and general molding techniques.
Yet a further object is to provide polyphenylene ethers with imide linking units which may be used for adhesive bonding.
Another object is to provide polyphenylene ethers with imide linking units which may be made into films.
Another object is to provide polyphenylene ethers with imide linking units which may be used in coating or laminating applications.
An additional object is to provide a process for making polyphenylene ethers with imide linking units which may be carried out under ambient reaction conditions.
Another object is to provide a process for making polyphenylene ethers with imide linking units which yields a final product in an imidized fused-glass state.